$n^2$ 暴力

#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
const int N = 20005;
int pos[N], a[N], ans, k, n, t;
int main() {
//	freopen("build.in", "r", stdin);
//	freopen("build.out", "w", stdout);
	scanf("%d%d", &t, &n);
	for (int cnt = 1; cnt <= t; cnt ++) {
		int sum = 0;
		for (int i = 1; i <= n; i ++)
			scanf("%d", a + i), pos[a[i]] = i;
		for (int i = 1; i <= n; i ++)
			for (int j = i + 1; j <= n; j ++) {
				if (a[j] + (a[j] - a[i]) > n || a[j] + (a[j] - a[i]) < 1) continue;
				int l = pos[a[j] + (a[j] - a[i])];	
				if (a[j] - a[i] == a[l] - a[j] && i < j && j < l)
					sum ++;
			}
		if (sum > ans) ans = sum, k = cnt;
	}
	cout << k << ' ' << ans << '\n';
	return 0;
}

考试的时候没有判 $>0$ ，全 $\WA$ qwq